foo.cc: In member function 'void Array::input()':
foo.cc:12:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%s",a);
    ~~~~~^~~~~~~~
foo.cc:13:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%s",b);
    ~~~~~^~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。